The shoulder joint’s unique structure allows for a full range of motion, Elizabeth Tracey reports


The shoulder joint is known as a ball and socket, where the ball is part of the arm bone called the humerus, while the socket is part of a bone known as the scapula. Edward McFarland, head of shoulder surgery at Johns Hopkins, says the tendons surrounding the joint are of paramount importance, forming a structure called the rotator cuff.

McFarland: Pretty much all of your rotator cuff tendons they’re about as thick as your little finger, maybe as wide as two fingers, and there's one in the front of the ball, there's one on the top of the ball and there's two in the back, so they form a cuff of tendons around the ball. The rotator cuff helps to stabilize the shoulder by pulling it into the socket. When your arms are in real close the ball doesn't really need to be held into the socket real tightly but if your arm is away from your body and you're picking something up the ball actually has to become compressed into the socket. You need the rotator cuff primarily for strength of the arm and the ability to lift things do things far away from your body and over shoulder height.  :33

McFarland says most adults will have shoulder issues at some point simply because of the large range of motion possible for the joint. At Johns Hopkins, I’m Elizabeth Tracey.